The objective of this Phase I proposal is to further develop and evaluate a novel method for radiolabeling monoclonal antibodies with technetium-99m for the specific diagnosis of cancer. The method provides for a very efficient uptake of offered technetium to the high specific activity required for radioimaging. Antibody prepared according to the described method retains most if not all of its immunoreactivity and no detectable denaturation or aggregation is observed. Stability of the prepared antibody is poor, however, losing its ability to complex technetium within 24 hours. This proposal details two potential methods for gaining the required stability for radiopharmaceutical "kit" formulation. Further, the proposal provides for a thorough evaluation of the technetium labeled antibody with in vitro methods and in vivo with human tumor xenographs in mice and rats. The applicant specifically plans to achieve the following goals: (1) to develop a method for stabilizing the transient DTT effect on the antibody; and (2) to evaluate the DTT-treated antibody-Tc99m complex for efficacy in localizing melanoma xenografts in nude mice.